Powder coatings for film capacitors have been known and as one example of such coatings, a composition consisting of 70 to 80% of an epoxy resin (m.p. 80.degree.-100.degree. C.), 20 to 30% of a curing agent (acid anhydride) and 1 to 30% of other ingredients (e.g. a filler, a flame retardant and a cure accelerator) is described in JP-A-58-194324. (The term "JP-A" as used herein means an "unexamined published Japanese patent application".) These prior art epoxy resin based powder coatings have high storage stability and exhibit good free-flowing properties during coating operations. The surfaces of a film capacitor element that is solely composed of a dielectric film (e.g. polypropylene or polyester film), electrodes on both sides of the dielectric film, and lead wires attached to them, can be coated with these powders to fabricate a highly moisture-proof film capacitor. However, when the capacitor element is heated at 120.degree. C. during coating operations, the dielectric film is prone to thermal deformation, which results in low electrical capacitance.
The problem of thermal deformation can be solved by applying the coating powders with the capacitor element being heated at 90.degree.-100.degree. C. but then the powders will not be sufficiently fused to provide good adhesion to the surfaces of the capacitor element. In addition, the applied coating will not cure fast enough to be satisfactory for practical purposes. It has therefore been desired to develop a powder coating that retains the high moisture resistance, storage stability and free-flowing properties of the prior art products and which yet can be applied at lower temperatures of 90.degree.-100.degree. C.